Collaborative work over the Internet, as an alternative to actual face-to-face meetings, has been growing in popularity. Discussions and lectures can be held while individual participants are in geographically distant locations.
A major requirement for efficient collaborative work of this kind is the ability to view a common document—whether a text document, overheads for a lecture, or a multimedia presentation. This preferably includes the ability to allow all participants to examine the document, the ability to direct everyone's attention to a specific item or page of the document, and the ability to add annotations that are visible (and perhaps modifiable) by all participants in the meeting. Further distinctions are possible: (i) one can distinguish between “synchronous collaboration” and “asynchronous collaboration”; and (ii) one can distinguish between “one-way collaboration” and “n-way” collaboration. In “synchronous collaboration,” all collaboration activities occur online, and participants interact in real-time. In “asynchronous collaboration,” collaboration activities can occur at different times for each participant. In “one-way collaboration,” only one of the participants can manipulate the shared document—the others are just “along for the ride” (i.e., able only to view). In “n-way collaboration,” any of the participants can perform operations that are then visible also to all fellow participants.
Two approaches are commonly used to provide these abilities. The first approach is to use a universal document representation scheme and install on the workstations of all participants an application able to manipulate documents. In some cases, the application has been enhanced to support collaborative work. This is the more common approach. HTML is typically chosen as the representation scheme, and a web browser (e.g., Netscape or Internet Explorer) is the common application. But such a scheme has disadvantages: web browsers do not “abstract away” from workstation-specific issues, such as screen size and resolution. As a result, products may be unable, for example, to place a highlighter in the same spot in the document as viewed by all participants in a session, causing obvious confusion.
The other common approach—known as “application sharing”—assumes that there is not one application common to all participants. To solve that problem, a single workstation is chosen to run the application needed to manipulate the document. The user at that workstation manipulates the document directly. Each of the other users is presented with a dynamically-updated snapshot of the screen window displayed by the application on the workstation. The remote users are able to manipulate the joint document through the replication of low-level events (such as mouse motion and keyboard operation) from the remote user's computers (where the snapshot is shown) to the workstation (where the application actually runs). There are at least two shortcomings to this approach: (a) it can be expensive, in terms of bandwidth required to replicate the snapshot across all remote computers; and (b) it can create a substantial security risk, since the technology used to replicate low-level events can be used to give a remote user control over the workstation where the application runs.
There is thus a need for an approach that provides the better features associated with each of the above approaches, without their corresponding drawbacks.
Another requirement for efficient collaboration is the ability to audibly and/or visually interact with other participants in a session. Many of the collaborative applications presently available rely on a teleconference over regular telephone lines to provide this component of the meeting experience. Such an approach can be quite cumbersome, since it may require that the participants manage computers as well as telephones. Often only voices, and not visual images, are distributed. Some collaborative applications provide for the delivery of audio and video information over the same computer network used for the collaborative work. This leads to a much more “real” experience for the participants.
However, there remains a need for a solution that provides for scalable delivery of audio/video information, capable of adapting the a/v streams to the bandwidth available to each participant.